1. Technical Field
The present invention relates to an electronic timepiece.
2. Related Art
JP-T-2000-512014 discloses a timepiece that executes navigation to a destination site. The timepiece disclosed in JP-T-2000-512014 includes a GPS receiver that receives radio waves transmitted from GPS satellites (hereinafter referred to as “satellite signals”). The timepiece disclosed in JP-T-2000-512014 specifies a current site by executing positioning calculation using the satellite signals received by the GPS receiver. Then, the timepiece disclosed in JP-T-2000-512014 displays a distance from the current site to a destination site and a direction of the destination site and executes navigation to the destination site.
To execute positioning calculation using satellite signals, time information and orbit information included in the satellite signals are necessary. The satellite signals include information regarding schematic orbits of all the GPS satellites (hereinafter referred to as “almanac data”) and include information regarding detailed orbits of GPS satellites which are transmission sources of the satellite signals (hereinafter “ephemeris data”) as orbit information. The almanac data is updated once per day. The ephemeris data is updated once per two hours and a valid period is about 4 hours.
In general, an electronic device including a GPS receiver retains almanac data and ephemeris data when the electronic device receives the almanac data and the ephemeris data.
In a case in which both the almanac data and the ephemeris data retained in the electronic device including the GPS receiver are valid at the time of activating the GPS receiver, the electronic device including the GPS receiver starts positioning calculation after receiving time information without newly receiving the almanac data or the ephemeris data (hot start).
In a case in which only the almanac data is valid between the almanac data and the ephemeris data retained in the electronic device including the GPS receiver at the time of activating the GPS receiver, the electronic device including the GPS receiver newly receives ephemeris data, receives time information, and subsequently starts positioning calculation (warm start).
In a case in which both the almanac data and the ephemeris data retained in the electronic device including the GPS receiver are invalid at the time of activating the GPS receiver, the electronic device including the GPS receiver newly receives both of almanac data and ephemeris data, receives time information, and subsequently starts positioning calculation (cold start).
Therefore, in warm start and cold start, a time to first fix (TTFF) in which a GPS receiver is activated and a positioning calculation result is obtained is longer than in hot start.
Incidentally, in a timepiece that executes navigation using GPS, it is considered that a GPS receiver is not normally operated and the GPS receiver is sporadically operated according to a manipulation of instructing start of navigation in order to reduce power consumption.
In this case, however, when an interval of the manipulation of instructing start of navigation is long, there is a high possibility of a GPS receiver starting an operation at the cold start. Thus, it takes a long time to start the navigation. When the cold starts occurs many times, an operation time of the GPS receiver becomes longer. Consequently, power consumption increases.